The present invention relates generally to printed circuits and the attachment of electronic components thereto. More particularly the present invention relates to a method for the attachment of electronic components, such as large-scale integrated circuits, capacitors, resistors and the like, on metallized glass substrates having electric circuits printed thereon, and establishing an electrical connection between the electronic components and the electric circuit on the substrate.
The miniaturization of electronic components has presented challenges in terms of the development of relatively fast, relatively inexpensive methods for attaching miniature electronic components, such as capacitors, integrated circuits, computer chips, and the like, to printed circuit boards, especially metallized glass substrates having electronic circuits printed thereon.
One process for attaching electronic components to printed wiring boards is disclosed in U.S. Pat. No. 5,365,656 to ATandT (incorporated by reference herein). That patent utilizes electrically anisotropic conductive adhesives to attach the electronic devices to the printed wiring board and also to form conductive electrical interconnection between the leads or bumps of the electronic devices and the printed wiring board. The method comprises applying the adhesive on the printed wiring board, placing the printed wiring board on a platen, placing the electronic device into the adhesive in alignment with the conductors on the printed wiring board, placing a spacer on the platen to form a chamber around the printed wiring board, positioning a resilient stretchable membrane above the spacer, optionally applying a vacuum to the chamber to draw the membrane down into contact with the devices, applying a fluid under pressure to the membrane so as to force the contacts of the devices toward the conductors of the printed wiring board, and applying heat to the assembly to cure the adhesive.
The process disclosed in the ATandT patent presents difficulties in applying uniform pressure to the electronic devices when dealing with large-scale production, such as treating approximately 100 printed wiring boards at a time. Furthermore, the ATandT process does not provide the ability to apply different pressures to different electronic devices mounted to the same printed wiring board. Moreover, the ATandT process relies upon the application of heat to cure the adhesive, and heat can adversely affect delicate electronic components. The use of heat to cure the adhesive also results in extended curing times, thus reducing the overall productivity of the process.
Therefore, a need exists for a process that overcomes the problems associated with the prior art.
The present invention satisfies the above-described needs by providing a novel method for attaching electronic components to metallized glass substrates having an electric circuit printed thereon. The method comprises depositing a desired quantity of an uncured, ultraviolet radiation-curable, anisotropic conductive adhesive in a desired location on a metallized glass substrate having an electric circuit formed on a surface of the substrate. An electronic component having electrical contacts or bumps formed on a portion thereof is then applied to the uncured, deposited adhesive wherein the electronic component is oriented so that the electrical contacts or bumps are positioned in the adhesive and in register with desired portions of the electric circuit on the substrate. Sufficient pressure is then applied to the electronic component to render the adhesive selectively conductive at locations between the electric circuit and the electrical contacts or bumps on the electronic component and substantially nonconductive at other locations, such that the electrical contacts or bumps make an electrical connection with desired portions of the electric circuit. Then, the adhesive is cured by irradiating the adhesive with ultraviolet radiation of a sufficient flux to substantially cure the adhesive.
In an alternate embodiment of the present invention the method comprises placing a plurality of metallized glass substrates having an electric circuit formed on a surface of the substrate into a carrier. The carrier defines a plurality of cavities, each cavity being adapted to receive and retain a substrate therein. A desired quantity of an uncured, ultraviolet radiation-curable, anisotropic adhesive is deposited in a desired location on each of the substrates in the carrier. An electronic component having electrical contacts or bumps formed on a portion thereof is then applied to each of the deposits of uncured adhesive on each substrate wherein the electronic component is oriented so that the electrical contacts or bumps are positioned in the adhesive and in register with desired portions of the electric circuit on the substrate. Pressure is simultaneously applied to each electronic component in the carrier. The amount of pressure is sufficient to render the adhesive selectively conductive at locations between the electric circuit and the electrical contacts or bumps on the electronic component and substantially nonconductive at other locations, such that the electrical contacts or bumps make an electrical connection with desired portions of the electric circuit. Then, the adhesive is cured by irradiating the adhesive deposits with ultraviolet radiation of a sufficient flux and for a sufficient time to substantially cure the adhesive.
In another disclosed embodiment of the present invention, there is disclosed a process for mounting at least one electronic device having electrical contacts onto an interconnection substrate having electrical conductors so as to establish an electrical interconnection between the contacts and the conductors, the interconnection substrate being substantially transparent to ultraviolet radiation. The process comprises applying a quantity of uncured, ultraviolet radiation-curable, anisotropic adhesive over a region on the interconnection substrate, the region including conductors to be electrically connected to contacts of at least one electronic device. An assembly is formed of the at least one device and the interconnection substrate by placing the at least one device on the interconnection substrate such that the contacts of the at least one device are in alignment with the conductors in the region of the substrate. Pressure is applied to the at least one device so as to force the contacts of the at least one device toward the conductors of the substrate. The adhesive is irradiated with ultraviolet radiation from a source positioned below the substrate such that the adhesive forms an electrical and mechanical interconnection between the contacts of the device and the conductors of the substrate.
In still another disclosed embodiment of the present invention, there is disclosed a process for mounting a plurality of electronic devices each having electrical contacts onto a plurality of interconnection substrates each having electrical conductors so as to establish an electrical interconnection between the contacts and the conductors, the interconnection substrates being substantially transparent to ultraviolet radiation. The process comprises positioning a plurality of substrates in a carrier. A quantity of uncured, ultraviolet radiation-curable, anisotropic adhesive is applied over a region on each interconnection substrate, the region including conductors to be electrically connected to contacts of the devices. For each substrate in the carrier, an assembly is formed of the devices and the interconnection substrates by placing at least one device on each interconnection substrate such that the contacts of the devices are in alignment with the conductors in the region of the substrate. A die is positioned above the carrier, the die including a plurality of pressure pads, the pressure pads being disposed on the die such that the pressure pads contact the devices on the substrates when the die is positioned above the carrier. Pressure is simultaneously applied to said devices through said pressure pads so as to force the contacts of said devices toward the conductors of the substrates. The uncured adhesive on the plurality of substrates is irradiated with ultraviolet radiation from a source positioned below the substrates such that the adhesive forms an electrical and mechanical interconnection between the contacts of the devices and the conductors of the substrates.
Accordingly, it is an object of the present invention to provide an improved method of connecting electronic components to metallized glass substrates having an electrical circuit printed thereon.
Another object of the present invention is to provide a method of attaching different sized and shaped electronic components to the same metallized glass substrate having an electrical circuit printed thereon.
Another object of the present invention is to provide a method of attaching electronic components to metallized glass substrates having an electrical circuit printed thereon that does not involve exposing the electronic components to excessive amounts of heat.
A further object of the present invention is to provide a method of attaching electronic components to metallized glass substrates having an electrical circuit printed thereon using an ultraviolet radiation-curable, anisotropic conductive adhesive.
Yet another object of the present invention is to provide a method of attaching electronic components to metallized glass substrates having an electrical circuit printed thereon that is relatively fast and relatively inexpensive.
Still another object of the present invention is to provide a method of simultaneously attaching a electronic components to a plurality of metallized glass substrates having an electrical circuit printed thereon.
These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended drawing and claims.